505nm and 480nm diode RESULTS

[DrMario]

Hm, now that I would like to know the wavelength of the lasers I have (I can use a 1mW Helium-Neon laser as a reference if that's something I can trust), where can I find the 1,000 lines / millimeter diffraction grating sheet for the wavelength measurement (I will have to make it rather stiff with a substrate so I don't have to deal with the potential artifacts).

 

[paul1598419]

To use a diffraction grating to measure wavelength you don't need a reference. You do need to have a lot of room and a large flat surface and some basic math skills to figure it out. A garage seems to work best for the place to do it. You will also need a long tape measure as you will need to know the distances for several parameters. The grating can be found in an eBay search, but don't cheap out on the ones for $1.00. There is a link to several threads on exactly how this is done. I don't want to take the time to spell it all out when it has been done here so many times before.

Here is a link to one: https://laserpointerforums.com/f70/make-your-own-spectrometer-under-1-a-98640.html

 

[DrMario]

Thanks for the link, I will be looking into it.. I will try to find the glass diffraction grating plate or if I can't, I will try plastic one. As for Helium-Neon laser, that's so I can double-check my work if I have to as Helium Neon laser doesn't really shift its wavelength much compared to the diode lasers.

 

[Zom-B]

Back from holidays and at work the Ocean Optics JAZ has returned reconfigured and re-calibrated. I immediately put a 532 DPSS in it and it measures 533.5nm. Any thoughts?

 

[ultimatekaiser]

Using a helium neon laser as a reference is actually a good idea, The problem is is that in order for it to be a valid reference they have to all go in at exactly the same angle, which can lead to some complications depending on how you do it. Though overall it’s not hard just time-consuming. If you have a polarized helium neon laser you can actually just use a PBS cube without getting any back reflections into the diode.

Biggest complication is the degrees at which you get your spread vs the angle of rhe surface your output lands on

 

[paul1598419]

I use a known source to check my spectrometer before measuring diodes for wavelength. It is just a way to reassure myself that it hasn't drifted and is no longer accurate. I use a meter long fiber optic cable into a 25 um slit which helps to keep strange angles from acting on the grating and giving me an error. I suppose it is still a possibility, but haven't gotten any readings to suggest it.

 

[DrMario]

Ultimatekaiser, that would make sense as Helium-Neon lasers occasionally flip (my tiny MG LHR-640 Helium-Neon tube I got from Sam Goldwasser is a flipper - out of curiosity I used the SLR camera polarizer filter and saw the laser light switch between bright and dim each time the tube flips its polarization). I will have to try and find the polarization cube for this purpose (and probably attempt to tame this flipper).

As for DPSS shifting its wavelength, it is actually possible, in fact some expensive DPSS is thermally stabilized (Nd:YAG / Nd:YVO4 laser crystal and KTP / BBO crystal compound do expand when it's / they're hot, shifting its wavelength somewhat, although the blame's usually on the pump diode as the effect gets exacerbated there since the laser crystal's lasing wavelength is determined by the laser diode wavelength and you guess it, it gets doubled or muxed depending on DPSS itself (half that, or sum of the laser crystal lasing wavelength) - and direct-doubled diode laser is kind of hard to tame).

And since Sharp 505nm laser is kind of an experiment done by Sharp, I would be curious if I get an odd bird like with some folks' 480 - 488nm laser diodes.

 

[Singlemode Laser]

Like Paul nicely explained,
using a fibre is one key ingredient for consistent measurement since the fibre decouples the optical adjustment inside the spectrometer. The second one is a calibration with a known light source. It should be another stable laser or a calibration lamp (<100$ on ebay).

Based on datasheets from green DPSS they can vary in their WL by +/- 1nm.


Singlemode

 

[Zom-B]

I forgot about the angle dependency. I feel like such an amateur now. I repeated the measurement this time in an integrating sphere and sure enough my 532 DPSS now measures 532.6nm. Would that be within the tolerance of a DPSS?

 

[Singlemode Laser]

I forgot about the angle dependency. I feel like such an amateur now. I repeated the measurement this time in an integrating sphere and sure enough my 532 DPSS now measures 532.6nm. Would that be within the tolerance of a DPSS?

According to this specsheet:

https://www.thorlabs.com/drawings/bfc8d6636698521a-38E0B409-E7FC-1AEB-11016E9DED880949/DJ532-40-SpecSheet.pdf

+/- 1nm is within the specs.

Singlemode

 

[paul1598419]

Good to see you posting, Singlemode. We have some new diodes to play with on the way. I am looking forward to your compilation as I'm sure you are interested in mine. Take care, buddy. BTW, your Thorlabs link doesn't work. Just in case you want to fix it.

 

[Singlemode Laser]

Good to see you posting, Singlemode. We have some new diodes to play with on the way. I am looking forward to your compilation as I'm sure you are interested in mine. Take care, buddy. BTW, your Thorlabs link doesn't work. Just in case you want to fix it.

Yeah, I am exited like a child at Christmas. These new ones are exactly at the WL what I want for my lab setup and I already started writing a paper draft involving a laser system based on them. I plan to add some members of this forum into the acknowledgments

Singlemode

PS: The link should be fixed now

 

[paul1598419]

Me too. Can hardly wait to get started. I look forward to reading your paper on the new laser system. You were in my thoughts as this came to fruition.

 

[ultimatekaiser]

Good stuff! Lots of good news coming in lately. I’m actually busy myself fixing a bunch of coherent lasers. Exciting new year looks like.

 

[paul1598419]

That's awesome, Matt. Wish I could get my hands on one to repair, or better still, in good working condition. You'll have to do a review at some point. :yh:

 

[Zom-B]

PS: The link should be fixed now

Link still doesn't work, and url looks like a session key